1. Field of the Invention
The present invention relates to radio field strength meters, and more particularly to portable handheld units suitable for general use by home owners, office personnel, security specialists, antenna installers, flight crews, utilities and schools.
2. Description of the Prior Art
Modern day life is awash in radio signals from all sources. Lately there has been a concern that cell phone transmissions so close to the user""s body could be causing health problems. And not long ago people living near high-voltage transmission utility towers were concerned that the million-volt-plus lines could be sending out harmful radiation. People who fly in commercial airlines are aware that the flight crews want them to turn off their wireless phones and computers because emissions from them might interfere with the airplane""s navigation and communication systems.
On the other hand, covert transmitters can be eavesdropping on industrial, military, and personal secrets and field strength meters and other detectors have been used for years to sweep an area clean of such bugs.
Supposing that such radio transmissions exist is one thing, but in order to do something about it the user needs to be equipped with a device that can measure signal strength and help locate the source of transmissions. However, transmitters and other sources of radiation can emit signals over a very broad part of the radio spectrum. The part between 10-MHz and 4.5-GHz is where radio and TV transmitters, cellphones, microwave ovens, garage-door openers, ham radios, police and fire radios, and many other common devices operate. So the detectors need to have a broad frequency response.
At the same time, the sources can range in power output levels from a few microwatts to a megawatt. Covert bugs can try to operate at very low levels to conserve battery life and to avoid detection. Radio and TV stations can be licensed to operate as high as a megawatt. So the detectors also need to have broad dynamic sensitivity.
It is therefore an object of the present invention to provide a radiated electric-field meter that is easy to use.
It is another object of the present invention to provide a radiated electric-field meter that can be used in the dark or used serepticiously.
Briefly, a radiated electric-field meter embodiment of the present invention comprises high frequency and low frequency antennas connected to a pre-amplifier with manually adjustable gain. This feeds a linear-logarithmic amplifier/detector with a mode switch for logarithmic/linear operations. A standard panel meter provides an analog reading. Green and red LED panel, lights are fed opposite signals proportional to the detected field strength. As the measurements change from zero to full-scale, the relative intensities of the green and red LED""s change, providing a change in illumination proportional to field strength with the green LED fully illuminated at zero signal strength and the red fully illuminated at maximum signal strength. A silent vibrator can also be switched in to provide a vibrator indication of field strength and changes of field strength.
An advantage of the present invention is that a radiated electric-field meter is provided for easy operation.
Another advantage of the present invention is that a radiated electric-field meter is provided that is easy to use in the dark, from a distance, or unobtrusively.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the drawing figure.